Stabilization of phosphosulfurized hydrocarbons



j STABILIZATION or PHGSPHOSULFURIZED HYDROCARBONS Fred B.'Fiscl1l, Springfield, and Elmer B. Cyphers, Cran- 'ford, N. J., assign'ors to'StandardOil Development Company; a corporation of Delaware NoDrawing. Application "December 8, 1951, Serial No. 260,764

5 Claims. (Cl.- 252-32.7)

capable of carrying higher unitloads without failure of the lubricating film than are-lubricants which 'do not contain these elements. For example, certain hydrocarbon oils, such as 'bright stock lubricating oilsand related mineral lubricating oil base'stocks, may be treated United States PatentO ably, R willhave no more than about '15 more preferably below 10, carbon atoms. R may be an alkenyl'(olefin c), dialkenyl (di-olefinic), cycloalkenyl (cyclo-olefimc), alkaryl, or alkenylaryl orv the like radical. Typical alcohols include vinyl alcohol; allyl alcohol; geraniol; citronellol; benzyl alcohol; cinnamyl' alcohol; l-prop'yl, lphenyl alcohol; 1-pentene-3-ol; 3-butene-2=ol;'m=methylbenzyl alcohol, and the like.

- Unexpectedly, it :has been found thatneither the organic acid nor the alcohol alone is eifective forinhibiting' HzS evolution. Furthermore, the alcohol ester radical mustbe unsaturated or aromatic since the saturated alcohol ester of an unsaturated aliphatic acid isin effective. For example, cinnamic acid, ethyl cinnamate, geraniol and benzyl alcohol are inactive in suppressing HzS evolution from phospho'sulfurized lubricants. Ben-zyl acetate, geranyl acetate and the like are, on the other at relatively high temperatures with various phosphorus sulfides, especially P285, although P283, P483 and P487 and others or mixtures 'of these may also be used. Treatment is continued long enough to add substantial sulfur and phosphorus. The resulting reaction products have been. stabilized by treatment with bases, basic reacting materials, reactive olefinic hydrocarbons and the like. These materials stabilize lubricants containing the phosphorus sulfide-treated additive, reducing their corrosiveness' toward copper, reducing their tendency to evolve hydrogen sulfide '(HzS) and improving their odor.

The various methods of stabilizingv phospho-sulfurized materials, however, have as yet failed to provide a complete answer to the problem of H28 evolution. For example, it is frequently desired to store for considerable periods of time either the phospho-sulfurized material or oil concentrates of it prior to blending it intoa finished lubricant. Excessive H28 evolution often occurs during storage even though the material has been stabilized with one of the afore-mentionedtreating agents. Furthermore, lubricants containing certain of the treated additives will under some conditions evolve H28. This tendency leads to corrosion and odor difficulties, impairs the saleability of the product, and makes the lubricants unsuitable for use in sometypes of engines.

I It has been found, in accordance with the present invention, that the tendency of phospho-sulfurized lubricants to evolve hydrogen sulfide under storage conditions may be appreciably reduced by the presence of minor, inhibiting amounts of certain organicosters.

hand, quite efie'ctive. An ester 'of an unsaturated aliphatic acid may be used providing the ester radical derived from the alcohol is also unsaturated.

While the positionof the double bonds in the unsaturated ester is not particularly'critical, greater effectiveness=is aiforded by using a compound having at least one double bond separated from the carbonyl oxygen by at least one CH2 group and such compounds are preferred. However, those having a double bond in a conjugated, alpha-beta position with respect'to the carbonyl oxygen may be used efiectively.

The 'phosphosulfurized hydrocarbon is prepared by treating a substantially olefin-free hydrocarbon, having a viscosity aboveabout Saybolt seconds Universal (S. S. U.) at 210 F. with a substantial proportion of a phosphorus sulfide at an elevated temperature. The proportions of the phosphorus sulfide may vary from as little as 5% to as much as 25%, the preferred range being around 10% to 20% of thephospho'rus sulfide based" on the weight of the oil. The treating temperature employed isin the range of 375 to 475 F.; preferably in the range of 400 to 430 F. The hydrocarbon obviously must be of such type, including viscosity and boiling 'point, that it remains stable during the treatment. The time of treatment may vary somewhat, from as little as 1 hour to as much as 20 hours or more. The reaction'is preferably continued for several hours, for example 10 hours or so and until the oil has a phosphorus content of 2 to 4% or more-by weight and a sulfur con- These esters improve the stability of the'phospho-sulfurized materials per se and of their derivatives. The esters also effect improvements when the phospho-sulized material is used as an additive in lubricants in small concentrations.

The organic esters used are unsaturated alcohol esters of monocarboxylic, aliphatic acids. 7 They may be prepared by conventional means by esterifying the acid with a monohydric, unsaturated alcohol. For the purposes of the following description and claims, the terms unsaturated alcohol or unsaturated ester will refer to those having alcohol hydrocarbon radicals with at least one double bond. The double bond may be of the olefinic or aromatic type. The alcohol molecule may contain up to three, four or even more double bonds and preferably contains no acetylenic-type triple bonds.

The organic acids used in preparing the esters are preferably fatty acids in the lower molecularweight range, usually having below about 10 and'preferably elow about 6 carbon atoms. Typical acids are formic, acetic, propionic, isobutyric, n-valeric, and the like.

The unsaturated alcohols employed in preparing the esters may be primary, secondary or tertiary alcohols having the formula -ROH wherein the R radical is a hydrocarbon radical having at least'2 carbonatoms. I Prefertentof 5% ormore'by weight. The phosphorus content may be as high as 5 or 6% and the sulfur content as high as 10 to 12%, but treatment should not be extended 'to the point that the material becomes insoluble in the oil' base stock in which it is to be used. Ordinarily the upper limit. is about 5 to 6% for the phosphorus content'and about 9to 11% for sulfur. I

1 Preferred hydrocarbons for'phosphosulfurization are lubricating oil base stocks such as bright stocks having for example an S." S. U. viscosity at 210 F. in the range from about '120 to 250 Saybolt seconds. 'They maybe obtained, for example, by deasphalting, dewaxing, acidtreating, clay-treating, etc.," of various petroleum residua. The higher molecular weight paraflins, aromatics, cyclic aliphatics, alkaryl compounds, and the like, may be used. Petrolatums; waxes, solvent extracts of petroleum fractions, etc., are also suitable. On the other hand, the unsaturated esters are generally ineffective in inhibiting HzS evolution from phosphosulfurized olefinic materials such as those derived from terpenes.

The unsaturated ester of the present invention may be added to the phosphosulfurized hydrocarbon or-to an oil concentrate before storage or shipment. However, the hydrocarbon treated in the manner described .nor-

I mally shows a titratable acidity and is highly objectionable because of its fairly high degree of instability. 'In order to reduce this instability, which is evidenced also in a high degree of 'corrosivity toward copper and objectionable odor, the reaction product of the hydrocarbon and phosphorus sulfideispreferably at least partially stabilized by further treatment before adding'the unsaturated ester.

. For: example, thephosphosulfurized' oilmay' have a portion or substantially all of its titratable acidity neutralized by treatment with a suitablebasic reacting -comsuch as potassium or sodium hydroxide, lime, barium hydroxide, and the like. Other basic reagents such as ammonia, alkyl or aryl substituted ammonia, such as am1n es or guanidine and derivatives thereof, or other neutralizing' agents may be used. This reactionmay be carried out by treatment with the basic reagent 1n solid or solution form using elevated temperatures up to about 400 F. The phosphosulfurized material may also be treated with an esterifying agent such as an alcohol, phenol, mercaptan or the like. e

If desired, the phosphosulfurized product may be reacted with minor proportions, about 2 to 50 weight per cent based on the total material, of a suitably active olefinic hydrocarbon. By suitably active 1s meant that the olefinic material has the property of reacting with loosely bound sulfur in the phosphosulfilrized oil in order to help stabilize the composition against subsequent HzS evolution. The preferred olefinic hydro carbon materials to be reacted with the phosphosulfurized material include the terpenes, terpineol', and the like and such olefinic hydrocarbons as isobutylene, dnsobutylene and the more reactive of the analogous aliphatic and cycloaliphatic materials. 'In particular, a product sold commercially as Dipentene consisting primarily of a mixture of true dipentene with'its isomers and minor proportions of related products, maybe used.

The ingredients may be mixed together and heated at a suitable temperature until a product of improved stability is obtained. The soaking temperature and the soaking time will vary depending upon the particular 1ngredients used and upon the degree of stability required. In general soaking temperatures from as low as 60 to as high as about 400 F. and soaking times of from 1 to 10 hours may be employed, depending upon the tendency to evolve HzS gas and upon the degree of stability desired. More broadly, the time required for soaking may be as little as one-quarter of an hour to as much as 20 hours.

The amount of unsaturated ester added may be varied within the general range of about 0.1 to 5.0 weightper cent, based on the treated or untreated phosphosulfurized hydrocarbon. A preferred range is about 0.5 to 2.0 weight per cent. The phosphosulfurized hydrocarbon is added to lubricants or greases in amounts ranging from about 0.1 to 20.0 weight per cent, based on the lubricant, the specific amount depending on the ultimate use of the lubricant. For example, amounts below about 5 .0 weight per cent will generally suffice if detergency properties are needed. Proportions in the range of 5 to 20 weight per cent may be needed for gear lubricants and'the like for extreme pressure service.

The phosphosulfurized additive may be stored and shipped as such or in the form of a concentrate in an oil base stock containing from about 20 up to 50 or more weight per cent of the active ingredient. The concentrate is then used for dilution with the finished lubricant or grease.

The unsaturated ester may be added to the finished viscous lubricating oil after the phosphosulfurized material has been blended therein, particularly if the latter material is added to lubricants shortly after phosphosulfurization. The present invention has particular application, however, to the inhibition of the concentrated, treated or untreated phosphosulfurized material. I

The invention will be further illustrated by reference to the following examples:

Example A deasphalted, dewaxed, acidand clay-treated Panhandle bright stock having an S. S. U. viscosity of about 170 at 210 F. was treated in a nitrogen atmosphere with 17.5 weight per cent, based on the oil, of P285 for hours at a temperature of 425 F. The product was then filtered and was found to have phosphorus and sul-. fur contents of about 3.5 and 6.5 weight per cent, respectively. The above phosphosulfurized oil was then treated with 9.5 weight per cent of commercial dipentene at a temperature of 380 F. with stirring for 1.0 hour. Commercial dipetene contains about 31% dipentene, 39% terpinolene, 6% alpha-pinene, 10% para-'cymene, 7% alpha terpeneol, 5% A2,4(8)-p-menthadiene, and 2% residue. The material was then cooled to room temperature while blowing with nitrogen.

include the hydroxides, carbonates, or oxides of alkali or alkaline earth metals,

Product A was prepared by blending with the treated material 0.17 weight per cent of oil-soluble sodium petroleum sulfonate having a molecular weight of about 500 315d 0.67 weight per cent of barium tert-octyl phenol sul- Blends of Product A containing 1.0 weight per cent concentrations of various alcohols, acids, and esters were then prepared and tested for H28 evolution tendencies as follows: Four-ounce bottles were filled about threefourths full with the product and stoppered with a tin foil-covered cork. The bottle was then stored at room temperature. Periodically, the stoppers were removed, and a filter paper that had been dipped in saturated lead acetate solution just prior to the test was placed over the bottle opening. After 30 seconds, the test papers were removed, dried, and given an HzS Rating by comparison with a set of standards in which 0 represents no stain and 10 represents a heavy, black, metallic stain. Product A was also tested for purposes of comparison. The data are as follows:

The phosphosulfurized bright stock, even after treatment with dipentene, was unstable in its undiluted state. Various organic acids and alcohols were ineffective for suppressing HzS evolution or even tended to increase HzS evolution. The addition of esters derived from unsaturated alcohols gave prolonged protection. It should be emphasized that the above ratings are on the phosphosulfurized material per se, and that the improvements obtained were sufiicient to bring the rating of a finished lubricant containing relatively small amounts of the phosphosulfurized hydrocarbon to desirable low values.

It will be obvious to the skilled workman that other additives in addition to the additives mentioned heretofore may be used in the finished lubricant. Such additives include thickeners, viscosity index improvers, oxidation inhibitors, metal dcactivators, pour point depressants and the like.

What is claimed is: I

I. An additive composition for lubricants comprising a major portion of a phosphosulfurized, substantially nonolefinic hydrocarbon and stabilizing amounts of an ester of an aliphatic acid having less than about 6 carbon atoms and a monohydric, unsaturated alcohol having at least 2 and less than 10 carbon atoms, said amounts being sufficient to stabilize the material against substantial evolution of sulfur containing gases.

2. A composition in accordance with claim 1 wherein said acid is a fatty acid.

3. An additive for lubricants comprising a stabilized phosphosulfurized mineral lubricating oil base stock containing at least 2 weight per cent phosphorus and 5 weight per cent sulfur and minor quantities of an ester of a monocarboxylic acid having less than about 6 carbon atoms and a monohydric alcohol having at least one double bond and from 2 to less than 10 carbon atoms in the molecule sufficient to stabilize the material against substantial evolution of sulfur-containing gases.

4. A composition in accordance with claim 3 in which said phosphosulfurized oil has been stabilized by the addi-, tion of a basic reacting compound.

5. A'composition in accordance with claim 3 in which said phosphosulfurized oil has been stabilized by treatment with a reactive olefinic hydrocarbon.

6. A composition in accordance with claim 5 in which said acid is acetic acid. I

7. A composition in accordance with claim 3 in which said alcohol is geraniol.

8. A composition in accordance with claim 3 in which said alcohol is benzylalcohol.

9. A composition in accordance with claim 3 in which said alcohol is vinyl alcohol.

10. An additive composition for lubricants comprising a major portion of a phosphosulfurized, substantially non-olefinic hydrocarbon and stabilizing amounts of vinyl acetate said amounts being sufficient to stabilize the material against substantial evolution of sulfur-containing gases.

References Cited in the file of this patent Number UNITED STATES PATENTS 

1. AN ADDITIVE COMPOSITION FOR LUBRICANTS COMPRISING A MAJOR PORTION OF A PHOSPHOSULFURIZED, SUBSTANTIALLY NONOLEFINIC HYDROCARBON AND STABILIZING AMOUNTS OF AN ESTER OF AN ALIPHATIC ACID HAVING LESS THAN ABOUT 6 CARBON ATOMS AND A MONOHYDRIC, UNSATURATED ALCOHOL HAVING AT LEAST 2 AND LESS THAN 10 CARBON ATOMS, SAID AMOUNTS BEING SUFFICIENT TO STABILIZE THE MATERIAL AGAINST SUBSTANTIAL EVOLUTION OF SULFUR CONTAINING GASES. 